1. Field of the Invention
The present invention relates to a method and apparatus for manufacturing core yarn in the spinning rotor and an open end spinning machine in which staple fibers are fed to the rotor collection surface and are twisted around the axis of a core thread to form a core yarn having a substantially linear core.
2. Prior Art
Attempts to develop methods for production of a core yarn by spinning staple fibers onto a core thread using an open-end spinning machine have produced satisfactory results for some purposes, but either it has not been possible to obtain a high quality of spun yarn or the core thread has been twisted together with the fiber ring to form a sort of two-ply yarn instead of the fiber ring being twisted about the axis of a substantially linear core thread.
There have been a number of publications teaching use of a spinning rotor in which a core thread is carried axially through the rotor, and a staple fiber yarn formed from fibers supplied to the rotor fiber collection surface is thrown around the axially disposed core thread U.S. Pat. No. 3,445,993, JA No. 29,453/71, DL No. 88,001). The product of this process is a kind of twine having a stretched core thread and a helical staple fiber yarn wound around it, such as shown in FIG. 5 of U.S. Pat. No. 3,605,395.
The disclosure of U.S. Pat. No. 3,605,395 also teaches a process for guiding a core thread through the spinning rotor with sufficient slack to form a loop adjacent to the fiber collection surface whereby the core thread and the staple fiber yarn are entwined on the inside wall of the spinning rotor. In this case, both the core thread and the fiber yarn are twisted together and produce a yarn resembling a two-ply yarn.